Typekit Tweaker is a simple bookmarklet that lets you modify font previews on Typekit. You can read more about it here.
If you'd like to submit an improvement or bug fix, please fork the repo and send a pull request. You can report problems using the issue tracker.
The Chrome extension automatically loads the Typekit Tweaker toolbar whenever you look at a font on Typekit.
You can install Typekit Tweaker from the Chrome Web Store.